<template>
  <transition v-on="on">
    <slot></slot>
  </transition>
</template>
<script >
import { addClass, removeClass } from "./dom";

export default {
  name: "CollapseTransition",
  setup() {
    return {
      on: {
        beforeEnter(el) {
          addClass(el, "collapse-transition");
          if (!el.dataset) el.dataset = {};

          el.dataset.oldPaddingTop = el.style.paddingTop;
          el.dataset.oldPaddingBottom = el.style.paddingBottom;

          el.style.height = "0";
          el.style.paddingTop = 0;
          el.style.paddingBottom = 0;
        },

        enter(el) {
          el.dataset.oldOverflow = el.style.overflow;
          if (el.scrollHeight !== 0) {
            el.style.height = el.scrollHeight + "px";
            el.style.paddingTop = el.dataset.oldPaddingTop;
            el.style.paddingBottom = el.dataset.oldPaddingBottom;
          } else {
            el.style.height = "";
            el.style.paddingTop = el.dataset.oldPaddingTop;
            el.style.paddingBottom = el.dataset.oldPaddingBottom;
          }

          el.style.overflow = "hidden";
        },

        afterEnter(el) {
          // for safari: remove class then reset height is necessary
          removeClass(el, "collapse-transition");
          el.style.height = "";
          el.style.overflow = el.dataset.oldOverflow;
        },

        beforeLeave(el) {
          if (!el.dataset) el.dataset = {};
          el.dataset.oldPaddingTop = el.style.paddingTop;
          el.dataset.oldPaddingBottom = el.style.paddingBottom;
          el.dataset.oldOverflow = el.style.overflow;

          el.style.height = el.scrollHeight + "px";
          el.style.overflow = "hidden";
        },

        leave(el) {
          if (el.scrollHeight !== 0) {
            // for safari: add class after set height, or it will jump to zero height suddenly, weired
            addClass(el, "collapse-transition");
            // fix #968 collapse animation failure.
            // in vue3.0.4, transitionProperty is set 'none' to avoid 'v-leave-from' issue
            el.style.transitionProperty = "height";
            el.style.height = 0;
            el.style.paddingTop = 0;
            el.style.paddingBottom = 0;
          }
        },

        afterLeave(el) {
          removeClass(el, "collapse-transition");
          el.style.height = "";
          el.style.overflow = el.dataset.oldOverflow;
          el.style.paddingTop = el.dataset.oldPaddingTop;
          el.style.paddingBottom = el.dataset.oldPaddingBottom;
        },
      },
    };
  },
};
</script>
